Portable grinding machine



Jan. 11,1944. E` A. HALL. E'r Al. 2,338,763

PORTABLE GRINDING MACHINE n Filed Jan. 19, 1943 2 Sheets-Sheet 1 WMM `lan. ll, 1944. E, A. HALL ETAL PORTABLE GRINDING MACHINE 2 sneaks-sheet 2 Filed J'an. 19, 1943 ILE-5 Patented `l'an. 11, 1944 UNITED STATES PATENT OFFICE PORTABLE GRINDING MACHINE Application January 19, 1943, Serial No. 472,871

9` Claims.

'Ihis invention relates to balancing -means for precision tools, and particularly for valve seat grinders of the eccentric type and which, when in use, are mounted on and rise from a guide pilot above the valve seat.

In the use of valve seat grinders, it is necessary, with a greater part of the work now being done, to grind the Valve seats within 1/1000 of an inch of true, and it is therefore necessary to have the tool itself accurately balanced or held in accurately balanced relation in use in order to perform the required high precision work. This has been accomplished to some extent, but not with the high precision necessary, in tools of the offset motor type with manually manipulated means such as illustrated in U. S. Patent 1,955,183, or as shown at the top of the motor in Fig. 3 of the .drawings herein. Such means have not, however, been entirely satisfactory, as the eccentric grinding action of the tool generates varying forces lateral to the tool, the changes of which cannot be responded to quickly enough by "he operator in his balancing control to effect necessary trueness of the grinding. In other lrds, in the use of an eccentric grinding tool of this character, as heretofore used, the tool body has a gyratory movement about a substantially fixed axis which is that of the guide pilot, so that the lateral force exerted by the tool body against the balancing means is alternately toward and away from the operator, and it is irnpossible for him to respond quickly enough to such changing force to maintain the perfect balance required for high precision work.

The object of the present invention is the provision in a tool of the class described, of means which, when the tool is in use, causes the Agyratory movement of the tool body relative to the guide pilot to be about an axis concentric to that of the pilot, with the grinding wheel axis inclined thereto and intersecting therewith at a predetermined point which is fixed and with respect to which the balancing is effected either by locating the point at, or substantially at, the dynamic center of balance of the tool when such center falls in the axial line of the tool yabout which gyration takes place, or by locating such point in or'substantially in, the line of balancing force applied through the manually operated means.

Other objects and advantages of the invention will be apparent from the following detailed description, and from the accompanying drawings illustrating different embodiments of the invention, and in which- Figure 1 is an elevation of a machine embodying the invention in grinding relation to a valve seat and with parts in central longitudinal section, said machine having its dynamic center of balance falling in substantiallyy the axial line Aof the tool; Fig. 2 is a cross-section on the .line 2 2 in Fig. l; Fig. 3 is a side elevation of a rmachine embodying the invention and in operative grinding relation to a valve seat, with parts in central longitudinal section and parts broken away, said machine being vof the type wherein the dynamic center of balance of the tool is offset with respect to the axial jline of the tool; Fig. 4 is a cross-section on the line 4-4 in Fig. 3, and

.Fig 5 is a fragmentary detail of the device illustrating its use for flat seat grinding.

In the drawings, I designates a section of an engine cylinder block, 2 a valve seat in said block, 3 a valve rstein guide in the block concentric to the valve seat, 4 a pilot mounted in said guide and projecting at its upper end through and above the valve seat, and 5 a grinding wheel forming a part of the tool and held in .proper eccentric grinding relation to the valve seat when the tool is mounted on the pilot, as understood in the art. While the Valve seat, in the present instance, is shown as located in easily accessible position on the block I, it may be positioned in a less accessible position such, for instance, as at the bottom of a cylinder, as is customary in airplane engines, so that grinding must be effected down through the cylinder.

In Fig. 1 the grinding machine is of the type wherein the dynamic center of balance is located on the axis of the pilot 4 and includes a body A from which a rotatable pilot receiving shaft I0 and grinding wheel carrying spindle II extend in concentric relation one within the other.

The body A, in the .present instance, includes an electric motor III, the armature shaft I5 of which is hollow and disposed in 'coaxial relation to the shaft III and journaled in upper andlower bearings I6 in the motor housing I'I.

The housing I'I of the motor is extended below the lower bearing I6 to form a kdiierential power transmission case I8 from which the shaft I0 and spindle II project, and in Vwhich they are connected by suitable gearing to the motor shaft I5. In the present instance, the shaft III is xedly mounted at its upper end in a sleeve 20 that is journaled in a Vbushing 2| Within Va xed internal bearing part 22 of ,the case I8. The shaft sleeve 20 has a worm Wheel 23 mounted thereon within the case to. adapt the shaft to be driven from the .motor shaft, `as hereinafter described.

The spindle II ismounted around the shaft III concentric thereto and for relative rotary movements on spaced bearings '2 5, the upperof which has its inner race bearing against the lower end of the sleeve ZI) while a sleeve 2S is disposed on the shaitbetween the inner races of the two sets of bearings and serves to hold them in properly spaced relation. The inner race of the outer bearing 25 seats at its outer or lower end on an annular shoulder 2l provided on the shaft I0 short of its lower end, The lower end of the spindle li has a reducing sleeve or nipple 28 threaded or otherwise suitably mounted thereon to turn with the spindle and forming a hollow` stud at its outer end on which the hub of the grinding wheel 5 may be mounted and iixedly secured by threading or in any other suitable manner.

The upper or inner end of the spindle II projects into the lower end of the case I8 and is provided therein with a spur gear 3i). A countershaft Si is journaled in the case I8 in parallel relation to the axis of the shafts I and I5, and at its upper end carries a spur gear 32 in mesh with a drive pinion 33 on the lower end of the motor shaft I and at its lower end carries a spur gear 34 in driving mesh with the spindle gear 30. Mounted on the shaft 3i intermediate the gears 32 and 34 is a worm gear 35 in driving connection with the worm wheel 23 on the shaft I0 through an intermediate worm gear 36 mounted on a cross shaft 3l within the case. The driving connection between the motor shaft I5 and the gears 23 and 30 is so proportioned that the wheel carrying spindle il will be driven at a high speed for grinding purposes, while the shaft I0 will be driven at a relatively slow speed.

For the purpose of the present invention, the shaft IB is provided longitudinally with a pilot receiving bore 45, the axis a of which is slightly inclined with respect to the turning axis b of the shaft and intersects the axis a at or substantially at the point 4I which is the dynamic center of balance of the machine and located, in the present instance, at the lower end portion of the armature shaft I5. Due to this divergence of the axes a and b, the axis of the grinding wheel 5, which coincides with the axis b, is eccentric to the axis a and the axis of the pilot 4 when the machine is mounted thereon. It is thus apparent that when a valve seat is being ground, the grinding wheel 5 will have engagement therewith at one side only of its axis, and that such point of engagement is progressively advanced around the valve seat by a turning of the shaft I0 within and relative to the spindle, such progressive movement being at a slower speed than the grinding speed of` the wheel. Inasmuch as the pilot 4 is stationary withy respect to the work, the revoluble movement of the wheel axis effected by a turning of the shaft lo is in the nature of a pendulum swinging from a point 4I, and this effects a corresponding revoluble swinging action of the machine body above such point except that when the lower end of the body is swinging in one direction the upper end is swinging in the opposite direction so that a balancing action is obtained.

The customary depth gauge rod 55 projects down through the hollow of the motor shaft I5 and into the upper end of the shaft I0, so as to have a bearing on the upper end of the pilot 4 when the shaft II) is mounted thereon, thus suspending the machine on the pilot with the grinding wheel in predetermined relation to the seat, as well understood in the art. The rod 5U passes down through an adjusting head 5I that is threaded on the upper end of the motor shaft I5 and is fixedly held in predetermined adjusted position in such head by a set screw 52. The gauge rod may be quickly moved to a desired positionof adjustment upon a loosening of the set screw 52 and may have a slow feeding adjustment imparted thereto by turning the head on the threaded end of the shaft. The head 5I is yieldingly held in adjusted position by a spring pressed detent 53 engaging a notched peripheral surface of the head. The lower end of the gauge rod 50 is held centered with respect to the shaft I0 by a bushing 54 mounted in an upper extended portion of the shaft.

The machine body is provided at one side with a lateral projecting handle 5E which may be grasped by the operator so that the machine, when in use, may be steadied and prevented from turning on the pilot.

In Fig. 3 the invention is illustrated in connection with a grinding machine of the unbalanced or offset motor or body type. In this form the motor housing 50 of the body has a side extension 6I forming a bearing for the upper end of the pilot receiving shaft 62 on which latter the grinding wheel carrying spindle 63 is mounted for free rotary movements. In the present instance the extension 6I has a bearing opening therethrough in parallel relation to the axis of the motor shaft 64, and the upper end of the shaft 62 has a bearing in this opening through an interposed sleeve 65. A spiral gear 66 is mounted for rotation in a recess 6I in the body extension 6I and is disposed around and keyed to the shaft 62 and sleeve 65 substantially midway between the ends of the latter. This gear is exposed at its inner side to a gear chamber 68 provided in the lower end portion of the motor housing. The sleeve 65 at its lower end bears against the inner race of the top bearing 'I for the spindle 63, and the upper end of the sleeve is engaged by a nut 1I which is disposed in an annular recess in the extension 6I and threads on the upper end of the shaft 62. A collar or shoulder 12 on the shaft 62 receives the lower end thrust of the inner race ring of the bearing 1li in opposition to the sleeve 65.

The spindle 63, which is concentric to the shaft 62 and mounted at top and bottom thereon through the bearings 10, has its upper end rotatably received in an opening 'I3 at the bottom of the extension 6I and provided at its top above the top bearing 'I0 with a spur gear I4 which is exposed to the gear chamber 68, in the present instance, has its hub portion threaded into the spindle end and bearing downward against the outer race ring of the adjacent bearing 10. The lower end of the spindle 63 extends below the lower bearing 'I0 and has a hollow grinding wheel carrying stud 'I5 threaded or otherwise secured thereon for turning therewith.

In the present instance the lower end of the motor shaft extends within the chamber 68V and carries a spur gear therein, which drives the spindle gear 'I4 through an intermediate pinion 8 I The pinion 8l is mounted on a vertically disposed countershaft 82, which shaft has a worm gear 83 in driving connection with the spiral gear 61 through an idler worm 84 that is mounted on a countershaft 85. It is thus apparent that the gearing communicates a high speed driving to the wheel carrying spindle 63 and a slow speed to the shaft 62 from the drive motor.

The lower end of the shaft 62, which is eX- tended through or into the hollow grinding wheel 5, is provided with a longitudinally extending bore 88 for closely receiving the guide pilot 4 of the work in a manner to prevent lateral play or tilting of the shaft thereon. For thepurposeof the present invention, this bore has its axis a' inclined slightly to the axis b of the shaft with the point of intersection of the two axes disposed at 9U which, in the present instance, is in line with the transverse thrust line of a manual balancing control C, as hereinafter described. The axis a of the shaft bore is 4concentric to that of the pilot 4 so that the axis of rotation of the shaft 62 and spindle 63 is slightly inclined to the pilot axis to the extent of divergence of the axis a, b. This causes the grinding'wheelto rotate about an axisthat is eccentric to or slightly offset from the pilot axis and also causes the axis of rotation of the wheel to have a revoluble movement about the pilot axis when the shaft 62 is rotated. It is apparent, however, that While the lower end of the machine or that adjacent to the seat being ground has a revoluble or orbital movement relative to the pilot, this movement is reduced to nil at the point 9B of intersection of the two axes a', b.

In the present instance, the bore BB is provided in a sleeve member 9! which is mounted in a bore or socket 92 in the lower end of the shaft 62 and projects below such shaft to form an extension thereof, and the inclination of the pilot receiving bore 8S relative to the axis of rotation of the shaft is obtained by inclining the bore in the sleeve rather than inclining the shaft bore 92 in which the sleeve is secured. The lower bearing 'lli is held in position by the lsleeve Qi `shouldering against the inner race ring in opposition to the end of the shaft 62, while the wheel carrying stud 75 is shown as bearing at its inner end against the outer race ring. It is apparent that the sleeve 9| may be fixedly mounted in the shaft bore to rotate on the pilot or mounted on the pilot to rotate in the shaft bore.

The shaft 62 lis hollow throughout its length to receive the depth gauge irod 95, which, when the machine is in use, is intended to bear at its lower end against the upper end of the pilot 4 to limit or gauge the feeding movement of the wheel to the work, as well understood in the art. This gauge rod projects above the upper end of the shaft and may be provided with the customary or any suitable feed control means. In the present instance, this means comprises an adjusting sleeve 95, secured in any desired position on the gauge rod by a set screw 91 and threaded at its lower end into a nut Si? which, in turn, is threaded into a receiving socket in the upper end of the body extension 6l in concentric relation to the shaft SZ. The sleeve 95 has a disk-like enlargement S9 at its outer end portion. The periphery of this enlargement is frictionally engaged by a spring finger mi] projecting from the machine body and is preferably notched to facilitate such engagement.

The tool balancing means C, which is for the same purpose as that of Patent 1,995,183, in the present instance, is shown as attached to the upper end of the motor housing 69 substantially in transverse alignment with the intersecting point Si) of the diverging axes a', br of the tool. This balancing means, in its present embodiment, is in the form of a handle comprising inner and outer telescoping members H and |06, with the inner member xeclly secured to and projecting transversely from the. upper `end portion of the motor housing and with the outer member normally held in yielding outwardly exten-ded relation to the inner member and forming the portion of the handle which is grasped by the operator. The inner member |05 is provided on its inner end portion with graduations (not shown) with which the inner end of the outer member registers to indicate when the outer member has been moved inward sufficiently on the inner member against the tension of the spring lill to balance the tool with respect to its point of bearing on the pilot and valve seat. This counterbalancing force imposed by the operator on said handle is preferably in line with the point 96 at right angles to the pilot axis. When the tool is in use the gyratory action of the grinding wheel axis is in the nature of a pendulum swinging in a circle from a suspending point 90, with such point stationary. It is thus apparent that the balancing means C is also substantially stationary when the device is in operation, at least so far as transverse movements thereof relative to the shaft axis are concerned, so that it is not necessary for the operator to vary the balancing pressure applied to the tool, first increasing it and then diminishing it a predetermined extent at each revolution of the shaft 5E about the pilot axis in order to maintain a constant uniform balance of the tool with respect to the work. With the present invention, wherein the axial point El? is in line with the balance thrust of the handle and is stationary, it is only necessary for the operator to exert sufficient thrust on the handle member il to move it into register with the indicated balance point on the handle member i235 and to maintain such position to effect a continued substantially perfect balance of the tool with lrespect to the work during a grinding operation and to effect very fine precision grinding.

It will be understood that the extent of projection of the wheel carrying spindle, and shaft in which it is mounted, from the head or major body portion of the machine depends on the particular work, such spindle and shaft usually being long, as shown in Fig. 3, when deep valve seats are being ground, and being relatively shorter, as shown in Fig. l, when surface seats are being ground. It will also be understood that the inclined feature of the pilot axis relative to the grinding wheel axis, as described herein, is not only important in obtaining a balanced action of the machine in use, but also in permitting flat face seats to be ground, due to the tilting of the grinding wheel relative to the valve seat, as best indicated in Fig. 5. It will also be understood that the sleeve 9| whether mounted in the outer shaft section for receiving the pilot or mounted on the pilot for entering the shaft bore, constitutes provision in connection with the shaft for operating or centering engagement with a stationary guide pilot, with the axis of the shaft and pilot diverging from a predetermined point remote from the tool carrying nature of the spindle.

We wish it understood that our invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of numerous modifications and changes without departing from the spirit of the claims.

Having thus described our invention, what we claim as new, and desire to secure by United States Letters Patent, is:

1. In a tool of the class described, a spindle and a shaft differentially rotatable about a common axis and having free outer ends and said spindle carrying a tool adjacent to its outer end, said shaft having provision for operating engagement at its outer end with a stationary guide pilot with the axes of the shaft and pilot diverging from a predetermined point spaced inwardly and remote from the outer end of the shaft whereby the spindle axis at the outer tool carrying end of the spindle has an orbital movement about the pilot axis in inclined relation thereto.

2. In a device of the class described wherein a shaft and a spindle are mounted in concentric relation one within the other for relative rotation and a grinding wheel is carried by the spindle adjacent to its outer end with the driving source for the shaft and spindle disposed inwardly from their outer ends, the provision in the outer end of the shaft in adjacent relation to the grinding wheel of a guide pilot receiving bore the axis of which is inclined to and intersects the shaft axis at a predetermined point which is spaced inwardly from the wheel with the divergence of said axes toward the outer end of the shaft whereby upon relative rotation of the shaft and spindle the spindle axis adjacent to the grinding wheel has a gyratory movement about the pilot axis and such movement of the device is reduced to substantially nil at the intersecting point.

3. In a device of the class described, a body having a shaft and a tool carrying spindle projecting therefrom at their outer ends for concentric independent rotation, a tool carried by the spindle adjacent to its outer end, said shaft having a guide pilot receiving socket in its outer end with its longitudinal axis spaced from that of the spindle at its tool carrying end and inclined thereto with the axes intersecting in predetermined relation to the body in inwardly spaced relation to the tool to reduce gyration of the body relative to that of the tool in use, said body having provision adjacent to the point of intersection of said axes for being grasped by an operator to hold the device during operation.

4. In a device of the class described, a body, a shaft and a spindle projecting at their outer ends from the body for concentric independent rotation, and a work engaging tool carried by the spindle at its outer end portion for rotation therewith, said shaft having provision at its outer end for centering engagement with a stationary guide to hold the shaft axis slightly inclined to that of the guide axis with thecpoint of intersection thereof spaced inwardly from the tool in predetermined relation to the body to gradually reduce the gyratory throw of the body inwardly from the tool when in use.

5. In a device of the class described, a body, a shaft and a spindle projecting at their outer ends from the body for concentric independent rotation, and a work engaging tool carried by the spindle at its outer end portion for rotation therewith, said shaft having provision at its outer end for cooperating engagement with a stationary guide to hold the shaft axis slightly inclined to that of the guide axis with the point of intersection thereof coinciding substantially with the dynamic center of gravity of the device and spaced inwardly from the outer end of the shaft, the divergence from said point being outward toward the point of carrying of the tool by the spindle.

6. In a device of the class described, a body, a shaft and a spindle projecting at their outer ends from the body for concentric independent rotation, and a work engaging tool carried by the spindle at its outer end portion for rotation therewith, said shaft having provision at its outer end for cooperating engagement with a stationary guide to hold the shaft axis slightly inclined to that of the guide axis with the point of inter.- section thereof spaced laterally from the dynamic center of gravity of the device and inwardly from the outer end of the spindle, and means operable to manually apply a balancing force to the body transverse to the shaft axis and substantially in line with said point.

7. In combination, a valve seat grinding device and a pilot for holding the device in operating relation to a valve seat to be ground, said device f having a spindle and a shaft concentrically mounted one within the other and differentially driven, a grinding Wheel carried at the outer end of the spindle, said shaft and pilot having interengaging connection in use with the turning axis of the shaft inclined to the axis of the pilot and intersecting therewith at a point without the valve seat being ground and inwardly of the device with respect to the grinding wheel whereby the wheel axis adjacent to the wheel has an orbital movement around the pilot axis during grinding, and means attached to the device adjacent to the point of intersection of said axes to be normally grasped for holding the device during operation.

8. In a valve seat grinder of the class described, a body portion, an abrasive wheel carrying hollow spindle extending from one end of said body, a shaft within said spindle rotatable relative thereto with its axis of rotation concentric to that of the spindle, said shaft having provision adjacent to the wheel carrying end of the spindle for coaction with a guide pilot to hold the device in predetermined relation to the work with the pilot axis inclined to and intersecting the shaft axis at a point inwardly remote from said wheel and inside of the body with said axes diverging outwardly from said point and toward the wheel and at a point which is approximately the dynamic center of gravity of the grinder, a motor in said body and means for connecting said motor to said shaft and spindle to drive them at different speeds, respectively.

9. In a valve seat grinder of the class described, a body portion, an abrasive Wheel carrying hollow spindle extending from one end of said body, a shaft within said spindle rotatable relative thereto with its axis of rotation concentric to that of the spindle, said shaft having provision adjacent to the wheel carrying end of f the spindle for coaction with a guide pilot to hold the device in predetermined relation to the work with the pilot axis inclined to and intersecting the shaft axis at a point inwardly remote from said wheel and inside of the body with said axes diverging outwardly from said point and toward the wheel and at a point which is approximately the dynamic center of gravity of the grinder, a motor in said body and means for connecting said motor to said shaft and spindle to drive them at different speeds respectively, and means operable to manually apply a balancing force to the body transverse to the shaft axis and substantially in line with said point.

ERNEST A. HALL. ROBERT S. BEVERLIN.

CERTIFICATE-OF CORRECTION. v V Patent No. 2,558,765. January l1, 19ML.

ERNEST A. HALL, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 2, second column, line )+95 after' "chamber 68 isert -and'; page 5, first column, line lO, for axis second occurrence, read --axes-F; line 61, for "Patent 1,995,185" read --Patent l,955,185; andthat the said Letters Patent should be read with this correction therein that the'same may con- `form to the record of the case in the Patent Office.

signed and sealed this 29th day of February, A. D. 19th.

`Leslie Frazer (Seal) Acting Commissioner of Patents. 

